Process and catalyst for dehydrogenation of hydrocarbons



olefins and diolefins. In

tion.

Patented Mar. 21, 1950 PROBESS AND CATALYST FOR DEHYDRO- GENA'IHON F HYDROCABBONS Alvle B. C. Dague andlohn W. Myers,

Bartlesville,

Okla, assignors to Phillips Petroleum Company, a corporation of Delaware No Drawing. Application July 16, 1M6, Serial No. 683,998

This invention relates to the catalytic dehydrogenation of parafiin hydrocarbons to produce one of its more specific aspects it relates to an improved process for the dehydrogenation of aliphatic paraifin hydrocarhons to produce the corresponding olefins and diolefins and is particularly applicable to the production of olefins and diolefins from aliphatic parafins containing from four to five carbon atoms per molecule. Another aspect of the present invention is the provision of novel catalysts for the catalytic dehydrogenation of paraffln hydrocarbons.

In the dehydrogenation of paraffins to the cor-.- responding diolefins, two dehydrogenation steps are customarily employed. In the first step the paramns are dehydrogenated to olefins which are then subjected in a second step to a separate dehydrogenation treatment to produce diolefins. The olefins may or may not be separated from the efiluent of the first dehydrogenation step prior to dehydrogenation to diolefins.

The customary procedure for the production of dioleflns by dehydrogenation of corresponding parafiins involves separate dehydrogenation of paramns and olefins using somewhat different conditions for each dehydrogenation reaction. The parafllns are first dehydrogenated to olefins in the presence of a highly active dehydrogenation catalyst, the olefins are separated from the eilluent of the paramn dehydrogenation step, and separately converted to the corresponding diolefin at a temperature somewhat higher and in the presence of a less active dehydrogenation catalyst than employed for the parafiin dehydrogenation step. Chromium oxide is the active dehydrogenation catalyst conventionally used for the dehydrogenation of paraflin but it is much too severe for olefin dehydrogenation. Separate dehydrogenation of parafiins and olefins requires the use of difiicult and relatively expensive separation steps to segregate the parafiin and olefin feed stocks, but the separation procedure is justified on the basis of improved yields and opera- In the dehydrogenation of paraflins some dioleflns are formed; however, the dehydrogenation of paraflins directly to .dioleflns is not practical by present dehydrogenation processes. Attempted combinations of concurrent dehydrogenation reactions involved in converting parafllns to diolefins in a single dehydrogenation step encounter serious difflculty due to the fact that optimum conditions forthe conversion of parafllns to olefins are quite difierent from the 56 8 Claims. ((71. 260-6833) 2. optimum conditions for the conversion of olefins to diolefins.

For the dehydrogenation of paraflins, such as normal butane, the catalyst ordinarily employed comprises approximately 10 weight per cent chromium oxide (CrzOa) deposited on a suitable carrier, such as aluminum oxide. As might be expected from the law of mass action, the dehydrogenation reaction is favored by low absolute or partial pressures. Low absolute pressures, i. e., below atmospheric pressure, while favorable to the dehydrogenation reactions, are undesirable in commercial operations due to the dimculty of preventing leakage of air into the system. For this reason it is customary to employ pressures somewhat above atmospheric pressure, generally in the neighborhood of about 30 pounds per square inch gage. A low partial pressure of the reactants, e. g., normal butane, may be obtained by dilution with an inert gas. It has been found that steam is undesirable as a diluent for .the dehydrogenation of parafiins since it poisons or reduces the activity of the chromium oxide catalyst of the conventional type. While other gaseous diluents, such as propane and lighter hydrocarbons, are not subject to this disadvantage they are generally not employed because the handling and recycling of large amounts of gaseous diluents represents a large item in plant investment and operating cost. The dehydrogenation of parafilns containing four or five carbon atoms per molecule may be conducted in the absence of a diluent with an efficient separation of olefin products from the paraffin recycle stock.

From the standpoint of chemical and physical characteristics, the most desirable diluent for dehydrogenation is water vapor. This diluent may be cheaply provided in any desired amount and may be removed from the hydrocarbon stream by simple condensation, thereby eliminating a large part of the compression and freetionation equipment necessary when other diluents are used. Steam has been used as a feed diluent in several different types of catalytic and thermal processes for hydrocarbon conversion such as cracking and olefin dehydrogenation. In such processes, particularly those in which solid catalysts are used, the steam serves not only as a diluent, but also as a reagent for the removal of carbon that deposits on the catalyst.

As mentioned hereinbefore, the use of water vapor has previously been condemned in the art ,because of its deleterious effects on the activity of conventional catalysts employed for the dehydrogenation of parafllns. The catalysts now used for the dehydrogenation of paraffins in commercial operations show poor conversion when steam is used as a diluent. Present practice is to dehydrogenate undiluted paraflins or to use a non-aqueous gaseous diluent. The feed stream is carefully dehydrated to eliminate all but traces of water vapor.

Steam dilution of feeds to dehydrogenation may be employed as a diluent in the dehydrogenation of paraffins, particularly normal butane, effectively and efiiciently with certain catalysts which are more fully disclosed hereinafter.

An object of this invention is to provide an improved process for the production of olefins and diolefins from corresponding parraflins. Another object of the present invention is to provide a process for the dehydrogenation of parafllns wherein steam or water vapor may be effectively and efficiently employed as the diluent. A more specific object is to provide a process which is particularly applicable to the dehydrogenation of butane to produce butylenes and butadiene. Still another object of the present invention is to provide catalysts which give eiiicient conversion of paraflins to olefins and diolefins in the presence of water vapor as a diluent. Other objects and advantages will become apparent to those skilled in the art from the following detailed disclosure of the invention.

We have found that paramns may be advantageously dchydrogenated in the presence of steam as a diluent to produce olefins and diolefins. Advantages obtained by steam dilution are longer reaction cycles, obviation of the necessity for using reactors made of special heat and corrosion resistant alloys, and the feasibility of using comparatively large reactors. The longer reaction cycles result from the chemical reaction of steam on deposited carbon, known as the water gas reaction, which enables the catalyst to be used for long periods without regeneration with an oxygencontaining gas. Large reactors of the bed type, in contrast to reactors comprising complex heat exchange systems, may be employed in this process as a result of the heat-carrying capacity of steam. This represents a tremendous saving in investment and operating costs.

We have also found that catalysts that are satisfactory for the dehydrogenation of undiluted paraiiins are relatively unsatisfactory for the dehydrogenation of parafiins diluted with steam; low yields and short process cycles are obtained. We have further found that a catalyst containing a major portion of alumina and a minor proportion of at least one oxide selected from the group consisting of molybdenum oxide, tungsten oxide, and vanadium oxide is satisfactory for dehydrogenating parafiins diluted with steam. Of these, vanadium oxide is preferred. The preferred content of the minor component is greater than 5 and less than 50 weight per cent of the catalyst. The catalyst may be further improved by the addition of from about 1 to about weight per cent chromium oxide as an activator. Contrary to expectations, the oxides of the alkali and alkaline earth metals as well as iron oxide, all of which are known promoters of the water gas reaction, decrease the effectiveness of the catalyst. Materials which promote the water gas reaction may, in some instances, be desirable as ingredients of the catalysts to increase the on-stream time or time between regeneration periods. The preferred catalysts are mixtures of aluminum oxide with a plurality of the oxides selected from the group consisting of molybdenum oxide, tungsten oxide, and vanadium oxide, and aluminum oxide admixed with chromium oxide and at least one of the oxides selected from the group consisting of molybdenum oxide, tungsten oxide, and vanadium oxide. Examples of preferred catalysts for use in the process of this invention are:

Weight per cent A1203 -90 M003 10-40 2 A1203 60-80 MOOc 10-30 V205 10-30 3 A1203 60-80 ClzOs 5-15 V205 10-30 The catalysts of this invention may be prepared by any of the methods of preparing solid porous oxide catalysts known in the art. Such methods include mixing of the powdered nongcl componrents, coprecipitation of the components as gel,

and inpregnation of the carrier material, i. e., aluminum oxide, with an aqueous solution of a salt of the other metal, with subsequent ignition to the oxide. An example of the latter method of preparation is the use of an aqueous solution of a molybdenum salt, preferaby ammonium molybdate, to impregnate a porous alumina carrier, suitably in the form of small pellets, followed by ignition to molybdenum oxide by passing an oxygen-containing gas over the catalyst at a moderately elevated temperature. The catalyst may be used in the form of granules of approximately 5 to 60 mesh size, in the form of pills or pellets, in the form of fluidized powder, or in the form of dust suspended in the feed.

In the operation of the present invention the paraffin feed, e. g., normal butane, is admixed with steam in the ratio of about 10 volumes of steam per volume of parafiin. The mixture is heated to the conversion temperature and passed into contact with the catalyst. The eliluent from the dehydrogenation zone may be processed in known manner for the separation of substantially pure olefins and diolefins. The olefins may be separately dehydrogenated in a known manner for conversion to diolefins. Unconverted paraiiins are recycled to the dehydrogenation step. If desired, the diolefins may be separated from the effluent and the olefins together with unreacted paraifins recycled to the dehydrogenation step.

Preferred conditions for dehydrogenation of before charging to the reaction zone or the steam may be separately injected at a plurality of points along the reaction zone. The steam is preferably preheated to a temperature at least as high as the temperature employed in the reaction and in some cases it may be preferable to separately preheat the hydrocarbons and the steam before mixing. It is sometimes desirable to preheat the steam to a temperature somewhat above the desired conversion temperature and to admix the preheated steam with preheated parafiin at a temperature slightly below the desired reaction temperature such that the resulting mixture attains the reaction temperature. The eilluent from the reaction zone is cooled to condense and remove steam, and the 'individual hydrocarbon components are separated by conventional methods such as fractionation, solvent extraction, and so forth. When the activity of the catalyst becomes undesirably low because of carbon deposition, the flow of hydrocarbons is interrupted, and steam is allowed to contact the'catalyst until the carbon is removed. Air may be added to the steam during the regeneration period if desired.

While the prior art states that steam is detrimental to the yield of olefins and diolefins in the dehydrogenation of parafiins, we have discovered catalyst compositions that are water resistant and especially suited to dehydrogenation of lyst for conversion of the feed to the desired products.

Example I An alumina-chromia-magnesia catalyst commonly used for. commercial dehydrogenation of undiluted normal butane, was used for the dchydrogenation of normal butane admixed with steam. The catalyst was in the form of pellets one-eighth inch in diameter and one-eighth inch in length with slightly rounded ends to prevent stacking. The composition of the catalyst in parts by weight (weight per cent) follows:

A1203 86 CrzOa 12 MgO 2 Two runs were carried out with' this catalyst with conditions and results shown below:

parafiins admixed with steam. In fact, we have found that with specific catalysts disclosed herein, the ultimate yield of olefins and diolefins is in some cases increased rather than decreased by use of steam. We have also found that it is not possible to predict from data on the dehydrogenation of parafiins without steam which catalysts will show the best yield when the paraflin hydrocarbon is admixed with steam. The following examples illustrate the processes of the present invention and illustrate the superiority of catalysts disclosed herein for dehydrogenation of paraffins in admixture with steam.

The catalyst of Example I is one which is commonly used for the dehydrogenation of anhydrous normal butane. In the subsequent examples, the catalysts were prepared by impregnating alumina pellets one-eighth inch in diame- While the per pass conversion is lowered by the larger quantity of steam, the ultimate yield or efliciency of the catalyst is slightly improved. This catalyst is much less efiicient for the dehydrogenation of normal butane in admixture with steam than it is for the dehydrogenation of undiluted normal butane as will be readily ap parent to those skilled in the art.

Ewample II ter and one-eighth inch in length with the solutions of salts of the respective minor components, followed by conversion of the salts to the corresponding oxides by ignition. In the several runs the steam was admixed with normal butane, the mixture preheated to the conversion temperature and passed over the pelleted catalyst. The eflluent was condensed and analyzed. The space velocity is expressed in terms of volumes of nor- The temperature of 1100" F employed in the dehydrogenation of undiluted normal butane was chosen for comparison as it represents approximately the optimum conversion temperature. At temperatures as high as 1200 F. excessive decomposition of undiluted normal butane takes place with poor yields of the desired products and poor catalyst efliciency. When steam is used as a diluent, higher temperatures are required for optimum conversion, other conditions being equal, than when undiluted normal butane is employed as feed.

The butadiene content of the butylenebutadiene yield for run 3 was 6.7 mol per cent.

These data show that higher ultimate yields are obtained with mixtures or normal butane and steam than with undiluted normal butane. This is contrary to the teachings of the prior art.

Example III Normal butane was admixed with steam, the mixture preheated, and passed into contact with a mixture of the oxides of aluminum and tungsten. The catalyst contained 85 weight per cent Example V To show the efiect of increasing the quantity of molybdenum oxide in the aluminum oxidemolybdenum oxide catalyst normal butane was dehydrogenated in the presence of a catalyst containing 60 weight per cent aluminum oxide and 40 weight per cent molybdenum oxide. In this run (Run 10) a mixture of 11.1 volumes of steam per volume of normal butane was heated to 1255 F. and passed into contact with the catalyst with a butane space velocity of 560. The total conversion per pass was 16.7 per cent with a per pass yield of butylenes and butadiene of 6.3 per cent and an ultimate yield of 38.0 per l5 aluminum oxide and weight per cent tungcent. The mixture of butylenes and butadiene sten oxide. The conditions and results were as contained 21.0 mol per cent butadiene. follows: This example shows that little, if any, advan- Yield of n-CaHH- Temp Space Vol. oi Vol. Ratio Total Con- 043:, mol percent Run OF butanemvoL/ Stgam to version pert V0 l. 11- 11 8110 teen pm pa Per Pass Ultimate This catalyst shows much higher yields than the chromia-alumina catalyst of Example I, but showed little increase in efficiency (as shown by the ultimate yield) with increased steam dilution.

Example IV tage is obtained in using more than about 10 weight per cent molybdenum oxide in the catalyst.

Example VI To determine the effect of chromium oxide in admixture with molybdenum and aluminum oxides, ternary mixtures of these oxides were made up. Mixtures of normal butane and steam were dehydrogenated under the conditions and with the results shown below:

Successive runs were made The catalyst of Run 11 contained weight per cent aluminum oxide, 30 weight per cent molybdeusing difierent steam to hydrocarbon ratios. The 50 num oxide, and 10 weight chromium oxide; that of conditions and results for n-butene are shown below:

Run 12, 50 weight per cent aluminum oxide, 25 weight per cent molybdenum oxide and 25 weight Yield of n-C4H|+ Tam Space Vel. Vol. Ratio Total Con- C H|, mol percent Run 0 of Butane, Steam version per voLlvoL/hr. n-Butaue pass, percent Per Pass Ultimate This example illustrates the superiority of this per cent chromium oxide. From the foregoing it appears that little advantage is gained by the use of the higher proportions of chromium oxide. This example illustrates the beneficial eiiect of molybdenum oxide in a chromiaalumina catalyst for dehydrogenation of paraffins in admixture with steam.

Example VII The catalyst of Example I was dipped in' a solution of ammonium molybdate and calcined to convert the ammonium molybdate to molybdenum oxide. In the dehydrogenation of noryield of butylenes and butadiene per pass 8.5,

tent. From the standpoint of catalyst life, it may be found economical in some instances to incorporate in the catalyst used in the process of our invention a minor proportion of a catalytic material known for promotion of the water gas and ultimate yield of ibutylenes and butadiene reaction. 51.4. The butylene-butadiene mixture contained From the foregoing it is believed that many 1 11101 p Cent butadiene- This example advantages obtainable from the practice of the ther illustrates the value of molybdenum oxide present invention 111 be readily apparent, t perin a chroma-alumina Catalyst for dehydrogenasons skilled in the art. However, since certain tion of parafiins in the presence of steam. This changes may be made in carrying out the above example also shows that magnesium oxide supmethod without departing from the scope of the presses the production of butadiene. invention as defined by the appended claims, it is intended that all matter contained herein shall Example be interpreted as illustrative and explanatory, Mixtures of the oxides of aluminum, chromium, rather t in a limiting sense vanadium and molybdenum were prepared. Mix- We claim; 5 tures of steam and normal butane were assed 1, A process for the dehydrogenation of an Ov r the C ta y s With the Conditions and aliphatic paraflin hydrocarbon containing four to Sults indicated below: five carbon atoms per molecule which comprises ries c H 1 4 11 4 5, 4 1m Run 'a g ttttlt i; $28 133? ig gt'r 11 551g;

vol./vol./hr. n-Butane moi I percent Per Ultipercent Pass mate The compositions of the catalyst in the weight contacting said hydrocarbon diluted with from per cent were as follows: 1 to volumes of steam per volume of hydrocarbon at a temperature within the range of from Run Aluminum Chromium Vanadium Molybdenum 3 about 1000 F. to about 1400" F. with a catalyst oxde consisting essentially of a major proportion of aluminum oxide and a minor proportion of at so 10 so 6O 20 2 least one oxide selected from the group consisting of molybdenum oxide, tungsten oxide and vanadium oxide, and a minor proportion of an activator The strikingly high yields and high efilciency of comprising h i oxjde the Catalysts Of this invention the dehydm 2. A process for the catalytic dehydrogenation genatlon of paramns diluted steam are of an aliphatic paraflin hydrocarbon containing brought out y thls examplefrom four to five carbon atoms per molecule Example 1X which comprises contacting said hydrocarbon diluted with from 1 to 20 volumes of steam per p catalyst. of Run of Example. VI volume of hydrocarbon at a temperature within taming the oxides of aluminum, chromium, and the range of from about F to about molybdenum was modified by the incorporation of various materials known to promote the water 1th a catalyst cons.lstmg e.ssentlauy Q gas reaction In one run the Catalyst was modi maJOr proportion of aluminum ox1de and a minor fled by dipping the pellets in a Solution of barium proportion of at least one oxide selected from chloride and calcining to convert the barium the gm?!) conslstmg f oxlde tung" chloride to barium oxide. The conditions used Stan oxlde and vanadlum and results obtained are shown in Run 11 of the .15 3. A pr ce r e catalytic dehydrogenation following table. The catalyst composition was of an al phatic para in h dr c b containing also modified by the incorporation of iron oxide in from four to five carbon atoms per c le a similar manner with the conditions and results which comprises contacting said hydrocarbon dishown in Run 18 of the following table: luted with from 1 to 20 volumes of steam per c stitis H '11 Total Coni a. cars a m 55191 vo1./vol./hr. n-Butane percent e Um- M li Pass mate This example shows that contrary to the teachvolume of hydrocarbon at a temperature within ings of the prior art, oxides whichare known to the range of from about 100 F. to about 1400 F. promote the water gas reaction do not increase with a catalyst consisting essentially of a major the efliciency of the catalyst, but on the other proportion of aluminum oxide and minor prohand, tend to decrease the efiiciency to some exportions of a plurality of the metal oxides selected from the group consisting of molybdenum oxide, tungsten oxide and vanadium oxide.

4. A process as defined in claim 1 wherein said paraffin hydrocarbon is normal butane.

5. A process for the dehydrogenation of an aliphatic paraflin hydrocarbon containing from four to five carbon atoms per molecule which comprises passing said hydrocarbon in admixture with from 1 to 20 volumes of steam per volume of hydrocarbon at a temperature within the range of from about 1000 F. to about 1400 F. into contact with a catalyst consisting essentially of a major proportion of aluminum oxide and a minor proportion of molybdenum oxide.

6. A process for the catalytic dehydrogenation of an aliphatic paraffin hydrocarbon containing from four to five carbon atoms per molecule which comprises contacting said hydrocarbon diluted with from 1 to 20 volumes of steam per volume of hydrocarbon at a temperature within the range of from about 1000 F. to about 1400 F. with a catalyst consisting essentially of a major proportion of aluminum oxide and minor proportions of chromium oxide and molybdenum oxide.

7. A process for the catalytic dehydrogenation of an aliphatic paraiiin hydrocarbon containing from four to five carbon atoms per molecule which comprises contacting said hydrocarbon diluted with from 1 to 20 volumes of steam per volume of hydrocarbon at a temperature within the range of from about 1000 F. to about 1400 F.

with a catalyst consisting essentially of a major proportion of aluminum oxide and minor proportions of the oxides of molybdenum and vanadium. 8. A process for the dehydrogenation of an aliphatic paraflln hydrocarbon containing from four to five carbon atoms per molecule which comprises passing said hydrocarbon in admixture with from 1 to 20 volumes of steam per volume of hydrocarbon at a temperature within the range of from about 1000" F. to about 1400 F. into contact with a catalyst consisting essentially of a major proportion of aluminum oxide and minor proportions of chromium oxide and vanadium oxide.

ALVIE B. C. DAGUE.

JOHN W. MYERS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,975,476 Pier et al Oct. 2, 1934 2,265,641 Grosskinsky et al Dec. 9, 1941 2,326,258 Schmidt et a1 Aug. 10, 1943 2,335,550 Sturgeon Nov. 30, 1943 2,356,697 Rial Aug. 22, 1944 2,397,352 Hemminger Mar. 26, 1946 2,401,802 Taylor et a1 June 11, 1946 Certificate of Correction Patent No. 2,500,920 March 21, 1950 ALVIE B. C. DAGUE ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 10, line 72, for 100 F. read 1000 F -i and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 11th day of July, A. D. 1950.

THOMAS F. MURPHY,

Assistant Commissioner of Patents. 

1. A PROCESS FOR THE DEHYDROGENATION OF AN ALIPHATIC PARAFFIN HYDROCARBON CONTAINING FOUR TO FIVE CARBON ATOMS PER MOLECULE WHICH COMPRISES CONTACTING SAID HYDROCARBON DILUTED WITH FROM 1 TO 20 VOLUMES OF STEAM PER VOLUME OF HYDROCARBON AT A TEMPERATURE WITHIN THE RANGE OF FROM ABOUT 1000*F. TO ABOUT 1400*F. WITH A CATALYST CONSISTING ESSENTIALLY OF A MAJOR PROPORTION OF ALUMINUM OXIDE SELECTED FROM THE GROUP CONSISTING OF MOLYBDENUM OXIDE, TUNGSTEN OXIDE AND VANADIUM OXIDE, AND A MINOR PROPORTION OF AN ACTIVATOR COMPRISING CHROMIUN OXIDE. 